Solvent and catalyst recovery technology in polyphenyl thioether production

Abstract

The invention relates to a solvent and catalyst recovery technology in polyphenyl thioether production, which comprises the steps of: after polycondensation reaction is finished, firstly adding 1-3mol/mol Na2S and fresh NMP (N-methyl pyrrolidone) solvent as a diluting agent, diluting the reaction system with NMP to obtain another mixture, and further treating the mixture by filtering, extraction, evaporation and spiral evaporator to respectively obtain a mixed solution containing NMP and water and a powder mixture containing a cosolvent and byproducts; and evaporating the mixed solution containing NMP and water to remove water to obtain NMP solvent containing certain impurities, further rectifying and purifying the NMP solvent by a rectifying tower to obtain NMP solvent with the purity of 99.98% and the recovery rate of 96-98%to be recycled for polyphenyl thioether resin synthesis, and treating the powder mixture containing the cosolvent and byproducts to obtain catalyst lithium chloride with the purity of 99.95-99.98% and the recovery rate of 98-99%.

Description

technical field [0001] The invention relates to the improvement of the production process of polyphenylene sulfide. Background technique [0002] Using sodium sulfide and p-dichlorobenzene (P-DCB) as raw materials, in the process of polycondensation production of polyphenylene sulfide (PPS) resin under the action of alkali metal co-solvent, alkali metal NMP (N-formaldehyde) is required in the polymerization stage base pyrrolidone) solution to complete the catalysis, compared with the cost of other raw materials, NMP and alkali metal co-solvent occupy a considerable price proportion, but in the production process of PPS, the solvent NMP and co-solvent are theoretically not consumed, therefore, can Whether to recover the still and co-solvent with a higher recovery rate is the key to reduce the production cost of PPS. [0003] After the polymerization reaction is completed, 65-70% of NMP can be recovered by conventional methods, but the remaining 25-30% is combined with co-sol...

AI Technical Summary

Problems solved by technology

[0003] After the polymerization reaction is completed, 65-70% of NMP can be recovered by conventional methods, but the remaining 25-30% is combined with co-solvent and remains in the residue, which is similar to complex Solid solution, boiling point 150-160, extremely difficult to separate, even under vacuum conditions, this part of NMP cannot be recovered

[0004] The Chinese patent application number CN001161423 introduces a solvent and co-solvent recovery technology in the production of polyphenylene sulfide, but it is puzzling that carbonate is used to reclaim the so-called catalyst, but in fact the recovery rate of this catalyst It is too low to be flattering, the catalyst recovery is very low, generally between 5-10%wt, and the recovered co-solvent cannot be reused at all

[0005] In the U.S. Patent No. US5711873, the recovery technology of the solvent produced by polyphenylene sulfide resin is introduced. Although this technology adopts low-boiling point solvent as the diluent of the reaction system, although adding a low-boiling point organic solvent in the reaction system helps the filtration of the reaction mixture , and low boiling point solvents are also easy to recover and purify. However, the requirements for the material of the polymerization reactor are relatively high. If it is added in the later stage of the reaction system, the pressure of the reactor will be increased. At the same time, it is necessary to always pay attention to the pressure of the reactor exceeding the design pressure. , so accidentally cause a serious accident